1. Technical Field
The present invention relates to linear regulators for integrated circuits, and more particularly to apparatuses and methods for providing regulated power to precision delay lines or elements.
2. Description of the Related Art
Linear regulators are employed in integrated circuits for regulating power voltage for delay lines or delay elements, which may be employed to protect from delay variations. Linear regulators are becoming more popular due, in part, to increased use of System-On-a-Chip (SOC) type semiconductor circuits. SOC devices generate many different kinds of voltage noise due to various macros or cores included in the SOC device. Since these systems typically have very delicate analog macros in the chip, very clean power is needed.
Linear regulator based delay lines suffer from bandwidth limitations because the linear regulators have to drive a large pass-gate transistor which provides a large amount of current needed for the delay line. Thus, to extend the bandwidth to higher frequencies, large amounts of decoupling capacitors are needed.
Referring to FIG. 1, a block diagram of a conventional linear regulator based delay line is shown. A linear regulator 10 includes a feedback loop 12, which includes an error amplifier 14, a pass device 16, a load 18 and a voltage reference 20. This regulator 10 provides high current to delay lines 22, but suffers from bandwidth limitations due to the fact the feedback loop 12 which consists of the error amplifier 14, the pass device 16, the load 18 and the voltage reference 20 have low bandwidth. The low bandwidth is due to the error amplifier 14 having to drive the large pass device (PFET) 16 which provides the current to a core or other device employing the regulated power. The low bandwidth results in higher frequency power supply fluctuation or noise being transferred to the cores or macros resulting in errors or higher power consumption.
Presently, many systems use very large decoupling capacitors 24 to regulate high frequency noise, but this has major disadvantages due to the fact that the capacitor 24 is very expensive to put on a chip due to its consumption of a large area. Decoupling capacitors can occupy areas of 40 microns by 40 microns or larger.
Thus, a need exists for improving the regulation of high-frequency noise and/or providing a higher bandwidth linear regulator.